As filed with the Securities and Exchange Commission on July 6,26, 2004

Registration No. 333-115553

SECURITIES AND EXCHANGE COMMISSION

AMENDMENT NO. 24
TO
FORM S-1
REGISTRATION STATEMENT UNDER
THE SECURITIES ACT OF 1933

ENERSYS
(Exact name of registrant as specified in its charter)

EnerSys
2366 Bernville Road
Reading, PA 19605
(610) 208-1991
(Address, including zip code, and telephone number, including area code, of registrant's principal executive offices)

Michael T. Philion
Executive Vice President—Finance
Chief Financial Officer
EnerSys
2366 Bernville Road
Reading, PA 19605
(610) 208-1991
(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

        Approximate date of commencement of proposed sale to the public:    As soon as practicable after this registration statement becomes effective.

        The registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this registration statement shall thereafter become effective in accordance with section 8(a) of the Securities Act of 1933 or until the registration statement shall become effective on such date as the Commission acting pursuant to such section 8(a) may determine.

The information in this prospectus is not complete and may be changed. We may not sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus is not an offer to sell these securities and we are not soliciting offers to buy these securities in any jurisdiction where the offer or sale is not permitted.

PROSPECTUS (Subject(Subject to Completion)

Issued ,July 26, 2004

12,500,000 Shares

COMMON STOCK

EnerSys is offering 12,500,000 shares of its common stock. This is our initial public offering and no public market exists for our shares. We anticipate that the initial public offering price of our common stock will be between $15 and $17 per share.

We have applied to list our common stock on the New York Stock Exchange under the trading symbol "ENS".

Investing in our common stock involves risks. See "Risk Factors" beginning on page 8.9.

PRICE$          PER SHARE

We have granted the underwriters the right to purchase up to an additional 1,875,000 shares to cover over-allotments.

As of the completion of the offering, assuming no exercise by the underwriters of their over-allotment option, no exercise of outstanding options since June 30, 2004 and the conversion of all outstanding shares of preferred stock into shares of common stock, investment funds affiliated with Morgan Stanley & Co. Incorporated, one of the representatives of the underwriters of this offering, will own 61.0% of our common stock.

The Securities and Exchange Commission and state securities regulators have not approved or disapproved these securities, or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The underwriters expect to deliver the shares of common stock to purchasers on                        , 2004.

                        , 2004

TABLE OF CONTENTS

        You should rely only on the information contained in this prospectus. We have not authorized anyone to provide you with information that is different. This prospectus may only be used where it is legal to sell these securities. The information in this prospectus may be accurate only on the date of this prospectus.

        This offering of common stock is only being made to persons in the United Kingdom whose ordinary activities involve them in acquiring, holding, managing or disposing of investments (as principal or agent) for the purposes of their businesses or otherwise in circumstances which have not resulted and will not result in an offer to the public in the United Kingdom within the meaning of the Public Offers of Securities Regulations 1995 or the UK Financial Services and Markets Act 2000 ("FSMA"), and each underwriter has only communicated or caused to be communicated and will only communicate or cause to be communicated any invitation or inducement to engage in investment activity (within the meaning of section 21 of the FSMA) received by it in connection with the issue or sale of the common stock in circumstances in which section 21(1) of FSMA does not apply to EnerSys, the issuer of such common stock. Each of the underwriters agrees and acknowledges that it has complied and will comply with all applicable provisions of the FSMA with respect to anything done by it in relation to the common stock in, from or otherwise involving the United Kingdom.

        The EnerSys common stock may not be offered, transferred, sold or delivered to any individual or legal entity other than to persons who trade or invest in securities in the conduct of their profession or trade (which includes banks, securities intermediaries (including dealers and brokers), insurance companies, pension funds, other institutional investors and commercial enterprises which as an ancillary activity regularly invest in securities) in the Netherlands.

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        Until    , 2004, all dealers that buy, sell or trade shares of our common stock, whether or not participating in the offering, may be required to deliver a prospectus. This delivery requirement is in addition to the obligation of dealers to deliver a prospectus when acting as underwriters and with respect to their unsold allotments or subscriptions.

        The trademark and trade names referred to in this prospectus are the property of their respective owners.

        We have provided certain statistics in this prospectus on the worldwide industrial battery business. Those statistics for North America are derived from information supplied by Battery Council International—which we refer to as BCI—and for Europe are derived from information supplied by the Association of European Storage Battery Manufacturers—which we refer to as EuroBat, and from management estimates. BCI and EuroBat are voluntary associations of battery manufacturers. BCI and EuroBat report data on a calendar-year basis. As a result, the 2003 market share data presented in this prospectus is not directly comparable to our 2003 fiscal year financial reports. In addition, BCI and EuroBat information only includes data for battery and charger sales, and does not include other products and service revenues. For geographic areas not covered by BCI or EuroBat, including South America and Asia markets, these statistics are derived from management's estimates. We believe these statistics are reasonable estimates. Market share data, however, are subject to change and cannot be verified with complete certainty due to limits on the nature, availability and reliability of raw data, the voluntary nature of the data gathering process and other limitations and uncertainties inherent in any statistical survey of market shares.

        In addition, we have provided data in this prospectus on trends in the telecommunications industry supplied by the Telecommunications Industry Association—which we refer to as TIA—from its 2004 Telecommunications Market Review and Forecast, ISBN 0-940919-48-6. TIA may be contacted directly at: 2500 Wilson Boulevard, Suite 300, Arlington, Virginia 22201; (703) 907-7770;www.tiaonline.org.

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PROSPECTUS SUMMARY

        This summary highlights information contained elsewhere in this prospectus. This summary may not contain all of the information that you should consider before deciding to invest in the shares of common stock. We urge you to read this entire prospectus carefully, including the "Risk Factors" and "Management's Discussion and Analysis of Financial Condition and Results of Operations" sections and our consolidated financial statements and the notes to those statements. The terms "EnerSys," "we," "our," and "us" refer to EnerSys—which is a holding company—and its consolidated subsidiaries. We use the term "the company" when we wish to refer only to the holding company and not to EnerSys and its consolidated subsidiaries. Our fiscal year ends on March 31. References in this prospectus to a fiscal year, such as "fiscal 2004," relate to the fiscal year ended on March 31 of that calendar year. For reading ease, certain financial information is presented on a rounded basis, which may cause minor rounding differences.

EnerSys Overview

        We are one of the world's largest manufacturers, marketers and distributors of industrial batteries. We also manufacture, market and distribute related products such as chargers, power equipment and battery accessories, and we provide related after-market and customer-support services for lead-acid industrial batteries. Industrial batteries generally are characterized as reserve power batteries or motive power batteries.

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Reserve power batteries are used to provide backup power for the continuous operation of critical telecommunications and uninterruptable power systems during power disruptions.



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Motive power batteries are used to power mobile manufacturing, warehousing and other ground handling equipment, primarily electric industrial forklift trucks.

        For 2003, we believe that we held approximately 24% of the worldwide market share in the lead-acid industrial battery business, with market shares of 30% in North America, 30% in Europe and 5% in Asia. For 2003, we believe that our worldwide market share of reserve power batteries was approximately 20% and in motive power batteries was approximately 28%. Our net sales for fiscal 2004 were $969.1 million, of which approximately 42% was attributable to the Americas, 53% to Europe, the Middle East and Africa, which we refer to as EMEA, and 5% to Asia. We report our financial results on a March 31 fiscal year basis.

        Our reserve power batteries are marketed and sold principally under thePowerSafe, DataSafeandGenesisbrands. Our motive power batteries are marketed and sold principally under theHawker, ExideandGeneralbrands. We also manufacture and sell related direct current—DC—power products including chargers, electronic power equipment and a wide variety of battery accessories. Our battery products span a broad range of sizes, configurations and electrical capacities, enabling us to meet a wide variety of customer applications. We manufacture reserve power and motive power batteries at 19 manufacturing facilities located across the Americas, Europe and Asia and market and sell these products globally in more than 100 countries to over 10,000 customers through a network of distributors, independent representatives and an internal sales force.

        We provide responsive and efficient after-market support for our products through strategically located warehouses and a company-owned service network supplemented by independent representatives.

Our Industry

        The size of the worldwide industrial lead-acid battery market in 2003 was $3.5 billion according to BCI, EuroBat and management estimates. The two key components of the industrial lead-acid battery market are reserve power batteries—a $2.0 billion market—and motive power batteries—a $1.5 billion market. The aerospace and defense market is an additional important sector of the battery industry, which is not included as a component of the $3.5 billion worldwide market information above.

        Reserve power batteries, also known as network, standby or stationary power batteries, are used primarily for backup power applications to ensure continuous power supply in case of main (primary) power failure or outage.

        For many critical systems, power loss, even for short periods of time, can result in loss of process control, massive data loss and significant financial liability. Reserve power batteries are essential for the continuous operations of communications providers, financial institutions, computer and computer-controlled systems and electric utilities.

        Motive power batteriesare used primarily to provide power for electric material handling and ground handling equipment. Motive power batteries are used primarily in electric industrial forklift trucks. Motive power batteries compete primarily with propane- and diesel-powered internal combustion engines.

Our Strengths

        We believe that our competitive strengths should enable us to expand our global market share and position us to achieve profitable growth. These strengths include:

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Our portfolio of leading brands with strong market positions;



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Our large installed base;



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Our global capabilities;



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Our broad range of products; and



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Our strong management team with a proven track record.

Our Strategy

        Our primary business objective is to capitalize on our competitive strengths to continue to expand our global market share, increase our net sales and improve our profit margins. We intend to achieve these objectives by implementing the following strategies:

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Expand our industry-leading position;



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Continue to expand into high-growth geographic markets;



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Further penetrate high-growth end markets;



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Continue to focus on manufacturing efficiency and cost reduction programs; and



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Pursue selective acquisitions.

Additional Considerations

        We operate in an extremely competitive industry and are subject to continual pricing pressure. We have been and may continue to be adversely affected by cyclical industry conditions and volatile raw materials costs. Because we use significant amounts of lead and acid in our operations, we are exposed to the risk of material environmental, health and safety liabilities. Many new energy storage technologies have been introduced, and we will need to acquire or develop products and technologies that will compete effectively in the future. For a discussion of these and other risks that you should consider before investing in our common stock, see "Risk Factors" beginning on page 8.9.

Our History and Recent Financing Activity

Our History

        EnerSys and its predecessor companies have been manufacturers of industrial batteries for over 90 years. Morgan Stanley Capital Partners teamed with the management of Yuasa Inc. in late 2000 to acquire from Yuasa Corporation (Japan) its reserve power and motive power battery businesses in North and South America. The acquired businesses included theExide, GeneralandYuasabrands. On January 1, 2001, we changed our name from Yuasa Inc. to EnerSys to reflect our focus on the energy systems nature of our businesses. In early 2002, we acquired the reserve power and motive power business of the Energy Storage Group, or ESG, of Invensys plc, whose principal brands wereHawker, PowerSafeandDataSafe.

Our Recent Recapitalization

        On March 17, 2004, we completed funding for a recapitalization. Prior to the recapitalization, we had $219.0 million of senior debt outstanding, including accrued interest, consisting of $177.6 million of term loans, a $17.0 million receivables facility and a $24.4 million revolving credit facility, with a weighted average interest rate of 4.3%. In order to extend the maturities of our outstanding debt, obtain greater financial flexibility, take advantage of favorable debt capital markets and historically low interest rates and provide liquidity to our existing stockholders, we entered into the following new financial arrangements:

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a $100.0 million senior secured revolving credit facility;



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a $380.0 million senior secured term loan B; and



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a $120.0 million senior second lien term loan.

        We used the proceeds of the senior secured term loan B and senior second lien term loan to refinance substantially all of our existing debt and pay accrued interest in the aggregate amount of $219.0 million, to fund a cash payment of $270.0 million to our existing stockholders and management and to pay transaction costs of $11.0 million. We intend to use a portion of the proceeds of this offering to repay the full amount outstanding under the $120.0 million senior second lien term loan and a portion of the amount outstanding under the $380.0 million senior secured term loan B. For additional information on our new financing arrangements, see "Description of Our Credit Facilities."

Principal Executive Offices

        Our principal executive offices are located at 2366 Bernville Road, Reading, PA 19605. Our telephone number at that address is (610) 208-1991.

Other Transactions and Relationships with Affiliates of the Underwriters

        We have engaged in a number of transactions with, and have other relationships with, affiliates of the representatives of the underwriters of this offering.

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Bank of America, N.A., an affiliate of Banc of America Securities LLC, is a lender under the senior secured term loan B and is committed to lend under our senior secured revolving credit facility. Additionally, itBank of America, N.A. acts as administrative agent and collateral agent under our credit facilities. Morgan Stanley Senior Funding, Inc. is committed to lend under our senior secured revolving credit facility and acts as syndication agent under our credit facilities, and Lehman Commercial Paper Inc. is committed to lend under our senior secured revolving credit facility and acts as documentation agent under our credit facilities. For additional information on our credit facilities, and the compensation payable under our credit facilities to these affiliates of our underwriters, see "Description of Our Credit Facilities" and "Certain Relationships and Transactions—Relationship with Morgan Stanley."



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Prior to this offering, investment funds affiliated with Morgan Stanley, which we refer to as the Morgan Stanley Funds, owned 17,279,122 shares of preferred stock, on an as-converted to common basis, and 10,729,423 shares of common stock, representing 77.0% of our outstanding preferred stock and 97.4% of our outstanding common stock. Giving effect to this offering, assuming no exercise by the underwriters of their over-allotment option, no exercise of outstanding options since June 30, 2004, and the conversion of all outstanding shares of preferred stock into shares of common stock, the Morgan Stanley Funds will own 28,008,545 shares of common stock, representing 61.0% of our outstanding common stock. See "Principal Stockholders."



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We have entered into a securityholder agreement with the Morgan Stanley Funds and our other principal stockholders. We have also entered into an indemnity and expense agreement with the Morgan Stanley Funds. See "Certain Relationships and Transactions" for a description of these agreements.

        As a result of the Morgan Stanley Funds holding 61.0% of our outstanding shares of common stock after giving effect to this offering, and their rights under the securityholder agreement, Morgan Stanley may be deemed to control our management and policies.

THE OFFERING

        References in this prospectus to the number of shares offered, and the number to be outstanding after the offering, do not include:

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1,875,000 shares that the underwriters may acquire upon exercise of their over-allotment option; and



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7,404,234 shares subject to outstanding options at a weighted average exercise price of $13.63 per share.

        Except as otherwise indicated, all information in this prospectus gives effect to:

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an initial public offering price of $16 per share, the mid-point of the filing range set forth on the cover page of this prospectus;



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the filing of our amended and restated certificate of incorporation;



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a 28.5-for-1 stock split that occurred on July ,9, 2004; and



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the conversion of all of our outstanding shares of preferred stock into an aggregate of 22,431,138 shares of common stock, effective at the closing ofimmediately prior to the offering.

SUMMARY CONSOLIDATED FINANCIAL, OPERATING AND PRO FORMA DATA

        The following tables set forth certain summary consolidated financial, operating and pro forma data. You should read the selected financial data presented below in conjunction with our consolidated financial statements and the notes to our consolidated financial statements included elsewhere in this prospectus and "Management's Discussion and Analysis of Financial Condition and Results of Operations." The summary consolidated financial data presented for each of the fiscal years in the three-year period ended March 31, 2004, and the balance sheet data at March 31, 2004, have been derived from our consolidated financial statements, which have been audited by Ernst & Young LLP, our independent registered public accounting firm.

        The summary pro forma as adjusted consolidated statement of operations for fiscal 2004 gives effect to the new financing arrangements we entered into in March 2004, and the anticipated use of the estimated proceeds of this offering as if such transactions had taken place on April 1, 2003. The summary as adjusted consolidated balance sheet as at March 31, 2004, gives effect to the anticipated use of the estimated proceeds of this offering as if it had taken place on March 31, 2004. See "Use of Proceeds" for information regarding our computation of the estimated proceeds of this offering.

        We are presenting this summary pro forma consolidated financial information for illustrative purposes only. This information is not necessarily indicative of what our operating results or financial position would have been if these transactions had taken place on the assumed dates or throughout the period presented, nor is it necessarily indicative of our future results of operations.

(1)

Includes the results of operations of ESG for the full years for fiscal 2003 and fiscal 2004, but only for nine days in fiscal 2002.

(2)

Reflects pro forma share data giving effect to the increase of 16,148,000 shares, which represents the number of shares that, when multiplied by an assumed offering price of $16, is sufficient to replace the capital in excess of earnings as a result of the distribution to stockholders of $258.4 million in connection with our recapitalization.

(3)

EBITDA is defined as earnings before interest expense, income tax expense, depreciation and amortization. EBITDA is not a measure of financial performance under accounting principles generally accepted in the United States and should not be considered an alternative to net earnings or any other measure of performance under accounting principles generally accepted in the United States as a measure of performance or to cash flows from operating, investing or financing activities as an indicator of cash flows or as a measure of liquidity. EBITDA has its limitations as an analytical tool, and you should not consider it in isolation or as a substitute for analysis of our results as reported under generally accepted accounting principles. Some of these limitations are:

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it does not reflect our cash expenditures for capital expenditures or contractual commitments;

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it does not reflect the impact of changes in effective tax rates or the use of net operating losses;

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although depreciation and amortization are non-cash charges, the assets being depreciated or amortized often will have to be replaced and EBITDA does not reflect the cash requirements for such replacements;

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it does not reflect changes in, or cash requirements for, our working capital requirements; and

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it does not reflect the cash necessary to make payments of interest or principal on our indebtedness.

Because of these limitations, EBITDA should not be considered as a measure of discretionary cash available to us to invest in the growth of our business. We compensate for these limitations by relying on our GAAP results as well as on our EBITDA and by carefully budgeting our projected cash requirements for interest, capital expenditures and taxes.

Our calculation of EBITDA may be different from the calculations used by other companies, and therefore comparability may be limited. Certain financial covenants in our senior secured credit facility and our senior second lien credit facility are based on EBITDA, subject to adjustments, and therefore EBITDA for purposes of these financial covenants may beis calculated differently from EBITDA

as shown above. Depreciation and amortization in this table excludes amortization of deferred financing costs, which is included in interest expense.

The following table provides a reconciliation of EBITDA to net earnings (loss):

We have included EBITDA primarily as a performance measure because management uses it as a key measure of our performance and ability to generate cash necessary to meet our future requirements for debt service, capital expenditures, working capital and taxes. Management also uses EBITDA to measure our compliance with important financial covenants under our credit facilities and to analyze our performance against our key public-company competitors, recognizing that the different ways in which different companies calculate EBITDA limits its usefulness as a measure of comparability.

(3)(4)

Special charges are discussed in detail in the notes to our consolidated financial statements and in "Management's Discussion and Analysis of Financial Condition and Results of Operations." The fiscal 2002 charges were primarily for the closures of a plant and certain other locations in the U.S. and our South American operations. The charges in fiscal 2004 related primarily to a settlement with Invensys, the recapitalization in March 2004 and costs of uncompleted acquisition attempts.

Recent Developments

        The following table shows selected unaudited operating results for our first quarter of fiscal 2005, compared to our unaudited results for the first quarter of fiscal 2004.

(4)(1)

ReflectsPro forma net earnings per common share and weighted-average share amounts have been calculated as if the offering of our common stock occurred on April 1, 2004. Accordingly, pro forma net earnings used to calculate pro forma earnings per share data giving effectexcludes Series A convertible preferred stock dividends of $8.1 million in the three months ended July 4, 2004. Pro forma weighted-average shares of common stock outstanding for purposes of the pro forma basic net earnings per share calculation consists of approximately 11,014,421 shares of common stock, converted preferred stock outstanding of 22,018,294 and 12,500,000 shares of our common stock being offered hereby.

        The increase in net sales in the first quarter of fiscal 2005 over the comparable period of fiscal 2004 was primarily due to theimproving global economic conditions. Both our business segments (reserve power and motive power) and all our regions (Americas, Europe and Asia) realized strong first quarter fiscal 2005 sales growth.

        The increase of 16,148,000 shares, which represents the number of shares that, when multiplied by an assumed offering price of $16, is sufficient to replace the capital in excess ofoperating earnings as a percent of net sales was a result of the distribution to shareholdersstrong growth in sales and tight control of $258.4 millioncosts, partially offset by increased raw materials costs and, in connection with our recapitalization.particular, lead.

RISK FACTORS

        You should carefully consider the risks described below before investing in our common stock. Our business is also subject to the risks that affect many other companies, such as technological obsolescence, labor relations and geopolitical events.

Risks Relating to Our Business

We operate in an extremely competitive industry and are subject to continual pricing pressure.

        We compete with a number of major domestic and international manufacturers and distributors of reserve and motive power lead-acid batteries, as well as a large number of smaller, regional competitors. Due to excess capacity in some sectors of our industry, consolidation among industrial battery purchasers and the financial difficulties being experienced by several of our competitors, we have been subjected to continual and significant pricing pressures. These pricing pressures have prevented us from being able to raise prices in response to increased costs and have resulted in overall pricing that has been flat to slightly down in the Americas and Europe. Prices in AsiaChina declined approximately 10% in fiscal 2004. We anticipate heightened competitive pricing pressure as Chinese and other foreign producers, able to employ labor at significantly lower costs than producers in the U.S. and Western Europe, expand their export capacity and increase their marketing presence in our major U.S. and European markets. Several of our competitors have strong technical, marketing, sales, manufacturing, distribution and other resources, as well as significant name recognition, established positions in the market and long-standing relationships with original equipment manufacturers and other customers. In addition, certain of our competitors own lead smelting facilities which, during periods of lead cost increases or price volatility, may provide a competitive pricing advantage and reduce their exposure to volatile raw material costs. Our ability to maintain and improve our operating margins has depended, and continues to depend, on our ability to control and reduce our costs. We cannot assure you that we will be able to continue to reduce our operating expenses, to raise or maintain our prices or increase our unit volume, in order to maintain or improve our operating results.

Cyclical industry conditions have adversely affected and may continue to adversely affect our results of operations.

        Our operating results are affected by the general cyclical pattern of the industries in which our major customer groups operate and the overall economic conditions in which we and our customers operate. For example, the significant capital expenditures made by the telecommunications industry during the period from fiscal 1999 through fiscal 2001, as numerous companies expanded their systems and installed standby backup battery power systems, drove demand for our reserve power products. As the telecommunications industry dramatically reduced building new systems in response to massive overcapacity, the demand for our reserve power products for this important application declined significantly. Both our reserve power and motive power segments are heavily dependent on the end-user markets they serve, such as telecommunications, uninterruptible power systems and electric industrial forklift trucks. A weak capital expenditure environment in these markets has had and can be expected to have a material adverse effect on our results of operations.

Our raw materials costs are volatile and expose us to significant movements in our product costs.

        We employ significant amounts of lead, plastics, steel, copper and other materials in our manufacturing processes. We estimate that raw materials costs account for approximately half of our cost of goods sold. Lead is our most significant raw material. The costs of these raw materials, particularly lead, are volatile and beyond our control. For example, average lead prices have increased from $0.2053 per pound during fiscal 2003 to $0.2773 per pound during fiscal 2004. The spot price of lead was $0.3937$0.4255 at June 30,July 23, 2004.

        Volatile raw materials costs can significantly affect our operating results and make period-to-period comparisons extremely difficult. We cannot assure you that we will be able to hedge our raw material requirements at a reasonable cost or to pass on to our customers the increased costs of our raw materials.

Our operations expose us to the risk of material environmental, health and safety liabilities, costs, and litigation.

        In the manufacture of our products throughout the world, we process, store, dispose of and otherwise use large amounts of hazardous materials, especially lead and acid. As a result, we are subject to extensive and changing environmental, health and safety laws and regulations governing, among other things: the generation, handling, storage, use, transportation and disposal of hazardous materials; remediation of polluted ground or water; emissions or discharges of hazardous materials into the ground, air or water; and the health and safety of our employees. Compliance with these laws and regulations results in ongoing costs. Failure to comply with these laws or regulations, or to obtain or comply with required environmental permits, could result in fines, criminal charges or other sanctions by regulators. From time to time we have had instances of alleged or actual noncompliance that have resulted in the imposition of fines, penalties and required corrective actions. Our ongoing compliance with environmental, health and safety laws, regulations and permits could require us to incur significant expenses, limit our ability to modify or expand our facilities or continue production and require us to install additional pollution control equipment and make other capital improvements. In addition, private parties, including current or former employees, could bring personal injury or other claims against us due to the presence of, or exposure to, hazardous substances used, stored or disposed of by us or contained in our products.

        Certain environmental laws assess liability on owners or operators of real property for the cost of investigation, removal or remediation of hazardous substances at their current or former properties or at properties at which they have disposed of hazardous substances. These laws may also assess costs to repair damage to natural resources. We may be responsible for remediating damage to our properties that was caused by former owners. Soil and groundwater contamination has occurred at some of our current and former properties and may occur or be discovered at other properties in the future. We are currently investigating and monitoring soil and groundwater contamination at certain of our properties, and we may be required to conduct these operations at other properties in the future. In addition, we have been and in the future may be liable to contribute to the cleanup of locations owned or operated by other persons to which we or our predecessor companies have sent wastes for disposal, pursuant to federal and other environmental laws. Under these laws, the owner or operator of contaminated properties and companies that generated, disposed of or arranged for the disposal of wastes sent to a contaminated disposal facility can be held jointly and severally liable for the investigation and cleanup of such properties, regardless of fault.

        Capital expenditures associated with environmental compliance were approximately $0.2 million, $1 million and $2.7 million in fiscal 2002, 2003 and 2004, respectively. Significant environmental capital expenditures over the prior two fiscal years are attributable to our ongoing ventilation improvement project at our Richmond, Kentucky facility. Capital expenditures for our Richmond, Kentucky ventilation improvement project were approximately $0.3 million and $1.3 million in fiscal 2003 and 2004, respectively. Our operating expenses associated with environmental, health and safety compliance are incorporated into our general operating expenses and are not separately quantified. However, we believe that we have not incurred material operating expenses associated with environmental, health and safety compliance over the last three fiscal years.

        We cannot assure you that we have been or at all times will be in compliance with environmental laws and regulations or that we will not be required to expend significant funds to comply with, or discharge liabilities arising under, environmental laws, regulations and permits, or that we will not be exposed to material environmental, health or safety litigation.

        In addition, recent legislation proposed by the European Union may affect us and the lead acidlead-acid battery industry. In November 2003, the European Commission issued a Directive that recommends the

elimination of mercury in batteries and the reclamation of spent lead and cadmium batteries for recycling (a "closed-loop" life cycle). On April 20, 2004, the European Parliament approved legislation that would effectively ban lead and cadmium in batteries as well as mercury, with the exception of batteries for which no suitable alternatives exist. While we do not believe that such alternatives currently exist, a suitable substitute for lead acidlead-acid batteries may be identified or developed. In response to the vote of the European Parliament, the European Commission stated it would not endorse a ban on lead or cadmium in batteries and affirmed its original proposal for closed-loop recycling regulations. The European Council, the main decision-making body of the European Union, is expected to comment on the new battery Directive within

the coming months. We cannot predict whether the Council will adopt the view of the Parliament or the Commission. Enactment and implementation of the European Parliament's Directive by the Member States could have a material adverse affecteffect on our business, results of operations and financial condition.

We are exposed to exchange rate risks, and our net income and financial condition may suffer due to currency translations.

        We invoice foreign sales and service transactions in local currencies, using actual exchange rates during the period. We translate our non-U.S. assets and liabilities into U.S. dollars using current rates as of the balance sheet date. Because a significant portion of our revenues and expenses are denominated in foreign currencies, changes in exchange rates between the U.S. dollar and foreign currencies, primarily the euro, British pound and Chinese renminbi, may adversely affect our revenue, cost of revenue and operating margins. For example, foreign currency depreciation against the U.S. dollar will reduce the value of our foreign revenues and operating earnings. Foreign currency depreciation against the U.S. dollar will result in a reduction of our net investment in foreign subsidiaries.

        Most of the risk of fluctuating foreign currencies is in our European operations, which comprised approximately half of our net sales during the last two fiscal years. The euro is the dominant currency in our European operations. The 14% appreciation in the value of the euro compared to the dollar during fiscal 2003 and 18% during fiscal 2004 had a significant impact on our reported results. Our sales in Europe were translated to the dollar at a rate 14.0% higher in fiscal 2003 than they would have been had the sales been translated at average exchange rates in effect in fiscal 2002, representing an increase of approximately $53.5 million; and were translated at a rate 17.0% higher in fiscal 2004 compared to average exchange rates in fiscal 2003, representing an increase of approximately $74 million.

        The impact of currency changes on our operating earnings is substantially similar as the impact on net sales. In fiscal 2003, operating earnings in Europe were approximately 17% higher than they would have been if translated at average exchange rates in fiscal 2002, representing an increase of approximately $4 million. In fiscal 2004, operating earnings in Europe were approximately 16% higher than they would have been if translated at the average exchange rates in fiscal 2003, representing an increase of approximately $5 million.

        The translation impact from currency fluctuations on net sales and operating earnings in the Americas and Asia is minimal, as virtually all net sales and operating earnings are in dollars or are pegged to the dollar.

        Foreign currency depreciation will make it more expensive for our non-U.S. subsidiaries to purchase certain of our raw material commodities that are priced globally in U.S. dollars. Significant movements in foreign exchange rates can have a material impact on our results of operations and financial condition. We do not engage in significant hedging of our foreign currency exposure and cannot assure you that we would be able to hedge our foreign currency exposures at a reasonable cost.

Our international operations may be adversely affected by actions taken by foreign governments or other forces or events over which we may have no control.

        We currently have significant manufacturing and distribution facilities outside of the U.S., including in the United Kingdom, France, Germany, China, Mexico, Poland, Spain, Italy and Canada. We may face political instability and economic uncertainty, cultural and religious differences and difficult labor relations

in our foreign operations. We also may face barriers in the form of long-standing relationships between potential customers and their existing suppliers, national policies favoring domestic manufacturers and protective regulations including exchange controls, restrictions on foreign investment or the repatriation of profits or invested capital, changes in export or import restrictions and changes in the tax system or rate of taxation in countries where we do business. We cannot assure you that we will be able successfully to develop and expand our international operations and sales or that we will be able to overcome the significant obstacles and risks of our international operations.

Our failure to introduce new products and product enhancements and broad market acceptance of new technologies introduced by our competitors could adversely affect our business.

        Many new energy storage technologies, other than lead-acid, have been introduced over the past several years. In addition, recent advances in fuel cell and flywheel technology have been introduced for use in selected applications that compete with the end uses for lead-acid industrial batteries. For many important and growing markets, such as aerospace and defense, lithium-based battery technologies have large and growing market shares and lead-acid technologies have decreasing market shares. Our ability to achieve significant and sustained penetration of key developing markets, including aerospace and defense, will depend upon our success in developing or acquiring these and other technologies, either independently, through joint ventures or through acquisitions. If we fail to develop or acquire, and to manufacture and sell, products that satisfy our customers' demands, or if we fail to respond effectively to new product announcements by our competitors by quickly introducing competitive products, market acceptance of our products could be reduced and our business could be adversely affected. We cannot assure you that our products will remain competitive with products based on technologies other than lead-acid.

We may not be able adequately to protect our proprietary intellectual property and technology.

        We rely on a combination of copyright, trademark, patent and trade secret laws, non-disclosure agreements and other confidentiality procedures and contractual provisions to establish, protect and maintain our proprietary intellectual property and technology and other confidential information. Certain of these technologies, especially in thin plate pure lead—TPPL—technology, are important to our business and are not protected by patents. For fiscal 2004, our net sales of products using thin plate pure leadTPPL technology were approximately $125 million. Despite our efforts to protect our proprietary intellectual property and technology and other confidential information, unauthorized parties may attempt to copy or otherwise obtain and use our intellectual property and proprietary technologies.

We may lose our right to use theExide trademark.

        Exide Technologies, during the course of its Chapter 11 proceedings, has sought to reject certain agreements related to the 1991 sale of Exide Technologies' industrial battery business to Yuasa, including the exclusive, perpetual, worldwide and transferable license to use theExide name on industrial batteries that we acquired in the Yuasa purchase. If the court were to find in favor of Exide Technologies, our license to use theExide name could be terminated.

        TheExide trade name is one of our better-known brands. OurExide-branded batteries represented approximately 12% of our net sales for fiscal 2004. We introduced testimony in the court proceedings from an expert witness who estimated that we would suffer damages of approximately $60 million over a seven-year period from price erosion, profit on lost sales and incremental rebranding expense in the event that the license were terminated. This expert's assessment of our damages assumed, contrary to our current belief, that the court would not delay the effective date of the termination.

        As with any litigation, the outcome of this proceeding is uncertain. We cannot assure you that we will retain the right to use theExide brand, even for a brief period of time, upon the resolution of this dispute by the court.

Relocation of our customers' operations could adversely affect our business.

        The trend by a number of our North American and Western European customers to move manufacturing operations and expand their businesses into Asia and other low labor-cost markets may have an adverse impact on our business. As our customers in traditional manufacturing-based industries seek to move their manufacturing operations to lower costlower-cost territories, there is a risk that these customers will source their energy storage products from competitors located in those territories and will cease or reduce the purchase of products from our manufacturing plants. We cannot assure you that we will be able to compete effectively with manufacturing operations of energy storage products in those territories,

whether by establishing or expanding our manufacturing operations in those lower-cost territories or acquiring existing manufacturers.

We may fail to implement our cost reduction initiatives successfully and improve our profitability.

        We must continue to implement cost reduction initiatives to achieve additional cost savings in future periods. We cannot assure you that we will be able to achieve all of the cost savings that we expect to realize from current or future initiatives. In particular, we may be unable to implement one or more of our initiatives successfully or we may experience unexpected cost increases that offset the savings that we achieve. Given the continued competitive pricing pressures experienced in our industry, our failure to realize cost savings would adversely affect our results of operations.

Quality problems with our products could harm our reputation and erode our competitive position.

        The success of our business will depend upon the quality of our products and our relationships with customers. In the event that our products fail to meet our customers' standards, our reputation could be harmed, which would adversely affect our marketing and sales efforts. We cannot assure you that our customers will not experience quality problems with our products.

We offer our products under a variety of brand names, the protection of which is important to our reputation for quality in the consumer marketplace.

        We rely upon a combination of trademark, licensing and contractual covenants to establish and protect the brand names of our products. We have registered many of our trademarks in the U.S. Patent and Trademark Office and in other countries. In many market segments, our reputation is closely related to our brand names. Monitoring unauthorized use of our brand names is difficult, and we cannot be certain that the steps we have taken will prevent their unauthorized use, particularly in foreign countries where the laws may not protect our proprietary rights as fully as in the U.S. We cannot assure you that our brand names will not be misappropriated or utilized without our consent or that such actions will not have a material adverse effect on our reputation and on our results of operations.

We may fail to implement our plans to make acquisitions.

        As part of our business strategy, we have grown, and plan to continue growing, by acquiring other product lines, technologies or facilities that complement or expand our existing business. We may be unable to implement this part of our business strategy and may not be able to make acquisitions to continue our growth. There is significant competition for acquisition targets in the industrial battery industry. We may not be able to identify suitable acquisition candidates or negotiate attractive terms. In addition, we may have difficulty obtaining the financing necessary to complete transactions we pursue. In that regard, our credit facilities restrict the amount of additional indebtedness that we may incur to finance acquisitions and place other restrictions on our ability to make acquisitions. Our failure to execute our acquisition strategy could have a material adverse effect on our business. The amounts we may pay for acquisitions are subject to limits on individual transactions and aggregate limits over the term of the credit facilities—until 2011 under the senior secured credit facility and until 2012 if we do not prepay in full the senior second lien credit facility. Our individual transaction limits are $25.0 million cash and $75.0 million

total (cash and company stock), and our aggregate limits are $100.0 million cash and $200.0 million total. Our ability to incur additional indebtedness also is restricted such that any significant acquisitions that could not be financed through cash generated from operations would need to be financed through issuance of additional company common stock. Exceeding any of these limitations would require the consent of our lenders. We cannot assure you that our acquisition strategy will be successful.

Any acquisitions that we complete may dilute your ownership interest in EnerSys, may have adverse effects on our financial condition and results of operations and may cause unanticipated liabilities.

        Future acquisitions may involve the issuance of our equity securities as payment, in part or in full, for the businesses or assets acquired. Any future issuances of equity securities would dilute your ownership interests. In addition, future acquisitions might not increase, and may even decrease, our earnings or earnings per share and the benefits derived by us from an acquisition might not outweigh or might not exceed the dilutive effect of the acquisition. We also may incur additional debt or suffer adverse tax and accounting consequences in connection with any future acquisitions.

        Where we are successful in completing acquisitions, we might experience difficulties in integrating the acquired business or assets. Acquisitions can entail planned write-offs and charges, as we attempt to realize synergies and cost reductions by restructuring our businesses to maximize the benefits of an acquisition, such as a portion of the special charges we recorded in fiscal 2002 in connection with the acquisition of ESG from Invensys. Acquisitions might result in unanticipated liabilities, unforeseen expenses and distraction of management time and attention. We recorded a charge of $24.4 million in fiscal 2004 to reflect a settlement of a number of issues with Invensys relating to the ESG acquisition, $20.0 million of which was attributable to the repayment of the notes we issued to Invensys—which we refer to as seller notes—in payment of a portion of the purchase price of ESG.

Implementation of a new enterprise resource planning system could adversely affect our operations.

        We are considering the implementation of a new enterprise resource planning (ERP) system in certain of our locations over the next five years to integrate the separate systems that we currently employ. An ERP system automates various business tasks including accounting, distribution and sales. Successful implementation of this system will be critical to our cost reduction initiatives and to our ability to comply with the financial reporting and internal audit compliance obligations of a public company. Integration and conversion of information from the systems to be replaced by this new system will significantly affect many aspects of our business, including our accounting, operations, purchasing, sales, marketing, and administrative functions, and could disrupt our business, distract management and increase our costs. If we were to experience difficulties or delays in the implementation of this new system, our ability to provide products to our customers on a timely basis could be adversely affected, which would harm our operating results and relationships with our customers. Additionally, any integration difficulties or delays could adversely affect the processing and reporting of our accounting and financial results. There can be no assurance that we would be able to correct any such difficulties or problems on a timely basis. Furthermore, there can be no assurance that, once successfully implemented, the new system will provide the intended benefits or that it will be adequate to support our operational needs.

Risks Relating to Our Substantial Debt and Our Liquidity

Our substantial indebtedness could adversely affect our financial condition.

        We have a significant amount of debt. On an as adjusted basis, calculated in accordance with our credit agreements, giving effect to the recapitalization that occurred on March 17, 2004, and our anticipated use of the estimated proceeds of this offering, we would have had $322.2$332.2 million of net debt outstanding on March 31, 2004, our ratio of net debt to adjusted EBITDAtotal capitalization on March 31, 2004, would have been 2.7 to 144% and our interest expense for fiscal 2004 would have been $21.4 million. Our significant amount of debt could have important consequences to our stockholders. For example, it could:

•

increase our vulnerability to adverse general economic and industry conditions, including interest rate fluctuations, because a significant portion of our borrowings bear and will continue to bear interest at floating rates;

•

require us to dedicate a substantial portion of our cash flow from operations to debt service payments, which would reduce the availability of our cash to fund working capital, capital expenditures or other general corporate purposes, including acquisitions;



•

limit our flexibility in planning for, or reacting to, changes in our business and industry;



•

restrict our ability to introduce new products or new technologies or exploit business opportunities;



•

place us at a disadvantage compared with competitors that have proportionately less debt; and



•

limit our ability to borrow additional funds in the future, if we need them, due to financial and restrictive covenants in our debt agreements; and



•

have a material adverse effect on us if we fail to comply with the financial and restrictive covenants in our debt agreements.

        We cannot assure you that we will generate sufficient cash flow to meet our debt service requirements, to fund our operations and meet our business plan, to take advantage of opportunities to acquire other businesses or to develop new products or penetrate new markets.

Restrictive covenants in our debt instruments may adversely affect us.

        Our financing arrangements contain a number of financial covenants, such as interest coverage and leverage ratios, and restrictive covenants that limit the amount of debt we can incur and restrict our ability to pay dividends or make other payments in connection with our capital stock, make acquisitions or investments, make capital expenditures, enter into sale/leaseback transactions, sell, buy or pledge assets and prepay debt. See "Description of Our Credit Facilities—Covenants," beginning on page 88,Covenants" for a discussion of these covenants.

        Our ability to comply with these financial covenants can be affected by events beyond our control, and we cannot assure you that we will be able to comply with those covenants. A breach of any of these covenants could result in a default under our financing arrangements. Upon the occurrence of an event of default under any of our financing arrangements, the lenders could elect to declare all amounts outstanding thereunder to be immediately due and payable and terminate all commitments to extend further credit. If the lenders accelerate the repayment of borrowings, we cannot assure you that we would have sufficient assets to repay the amounts due. Certain defaults, or the acceleration of any repayment obligation, under any of our material debt instruments would permit the holders of our other material debt to accelerate our obligations with respect to such other material debt.

Risks Relating to the Offering

The Morgan Stanley controlsFunds control us and itstheir interests could be in conflict with the interests of other stockholders.

        After giving effect to the offering, the Morgan Stanley Funds will own approximately 61.0% of our outstanding common stock. Two of our directors, Messrs. Hoffen and Fry, and two of our director nominees, Messrs. Hoffman and Elliott, currently are employees of Morgan Stanley. As a result of these relationships,the Morgan Stanley Funds' ownership interest in us, the Morgan Stanley Funds may be deemed to control our management and policies. In addition, the Morgan Stanley Funds may be deemed to control all matters requiring stockholder approval, including the election of our directors, the adoption of amendments to our certificate of incorporation and the approval of mergers and sales of all or substantially all our assets. Circumstances could arise under which the interests of the Morgan Stanley Funds could be in conflict with the interests of our other stockholders.

        Morgan Stanley and a new independent private equity firm, Metalmark Capital LLC, led by Howard Hoffen and senior members of Morgan Stanley Capital Partners, including Eric Fry and Michael Hoffman, have agreed that an affiliate of Metalmark Capital LLC will manage MSCP IV and certain of its related funds on a sub-advisory basis. This sub-advisory relationship is expected to commence in the third quarter of 2004. As a result of such agreement, Metalmark Capital LLC may be deemed to control our management and policies.

Certain of our underwriters may have conflicts of interest because an affiliate of one of the underwriters will receive part of the proceeds of this offering and because affiliates of oneanother of the underwriters own a majority of our outstanding common shares.

        One of the representatives of the underwriters—Banc of America Securities LLC—is affiliated with a lender under our credit facilities. We expect to use substantially all of the net proceeds of this offering to repay outstanding indebtedness under our credit facilities, including approximately $2.3 million that will be payable with respect to indebtedness owed to Bank of America, N.A., an affiliate of Banc of America Securities LLC. As a result, this underwriter may have a conflict of interest.

        In addition, oneanother of the representatives of the underwriters—Morgan Stanley & Co. Incorporated—may have a conflict of interest because of the ownership of a majority of our outstanding common shares by investment funds affiliated withthe Morgan Stanley.

We cannot assure you that we have implemented all required corporate governance and accounting practices and policies, including those required by the Sarbanes-Oxley Act and applicable SEC rules.

        Prior to this offering, as a privately-held company, we were not subject to any of the corporate governance and financial reporting practices and policies required of a publicly-traded company. We are in the process of implementing the controls and procedures, but cannot assure you that our audit controls and procedures will comply with all of these practices and policies. Implementation of these practices and policies could disrupt our business, distract our management and employees and increase our costs. If we

fail to develop and maintain effective controls and procedures, we may be unable to provide the required financial information in a timely and reliable manner.Stanley Funds.

We are a "controlled company" for purposes of the New York Stock Exchange listing requirements and therefore will opt out of certain corporate governance requirements.

        Because certainMorgan Stanley Dean Witter Capital Partners IV, L.P., one of the Morgan Stanley Funds, which we refer to as the MSCP Funds,IV, and our other existing institutional stockholders, will continue to hold more than 50% of the voting power of EnerSys after giving effect to the offering, we are a "controlled company" for purposes of the New York Stock Exchange listing requirements. As such, we have opted out of several of the NYSE's corporate governance requirements. Among other things, this means that our Board of Directors, our compensation committee and our nominating and corporate governance committee are not required to be independent. Morgan Stanley is acting as one of the representatives of the underwriters of this offering.

If a significant number of shares of our common stock are sold into the market following this offering, the market price of our common stock could significantly decline, even if our business is doing well.

        If a trading market develops for our common stock, the Morgan Stanley Funds, investment funds affiliated with J.P. Morgan, which we refer to as the J.P. Morgan Funds, certain entities affiliated with GM, which we refer to as the GM Shareholders,Stockholders, and Messrs. Craig, Philion, McManus, Zuidema and Shea, who will collectively own 72.8% of our shares upon completion of the offering, may elect to sell their shares of our common stock or exercise their stock options in order to sell the stock underlying their options. Sales of a substantial number of shares of our common stock in the public market after this offering could depress the market price of our common stock and impair our ability to raise capital through the sale of additional equity securities. Officers, directors, stockholders and stockholdersoptionholders owning substantially all of our shares, have agreed, subject to exceptions, that, without the prior written consent of the underwriters, they will not, directly or indirectly, sell any of these shares or exercise any of their options for 180 days after the date of this prospectus, subject to certain extensions. These agreements, however, can be waived by Morgan Stanley and Lehman Brothers in their sole discretion.

Our stock price could be volatile and your investment in our common stock could suffer a decline in value.

        There currently is no public market for our common stock. An active trading market for our common stock may not develop. If a trading market does develop, our stock price could be volatile. You may be unable to resell the common stock you buy at or above the initial public offering price. We will establish the initial public offering price through our negotiations with the representatives of the underwriters. You should not view the price they and we establish as any indication of the price that will prevail in the trading market.

The price at which shares of common stock are sold in the offering is significantly higher than our net tangible book value per share.

        The public offering price of our shares of common stock is significantly higher than the net tangible book value per share of our common stock. Purchasers of our common stock in this offering will experience immediate and substantial dilution in pro forma net tangible book value of $15.25 per share. Additional book value dilution is likely to occur upon the exercise of options. To the extent we raise additional capital by issuing equity securities, our stockholders may experience further substantial book value dilution.

SPECIAL NOTE ABOUT FORWARD-LOOKING STATEMENTS

        We have made forward-looking statements in this prospectus, primarily in the sections entitled "Prospectus Summary," "Risk Factors," "Management's Discussion and Analysis of Financial Condition and Results of Operations" and "Business." Forward-looking statements include the information concerning our possible or assumed future results of operations, business strategies, financing plans, competitive position, potential growth opportunities and the effects of future regulation and competition. Generally, you can identify these statements because they use words like "anticipates," "believes," "estimates," "expects," "future," "intends," "plans" or the negative of such terms or similar terms. These statements are only our current expectations. They are based on our management's beliefs and assumptions and on information currently available to our management.

        Forward-looking statements involve risks, uncertainties and assumptions. Although we do not make forward-looking statements unless we believe we have a reasonable basis for doing so, we cannot guarantee their accuracy. Actual results may differ materially from those expressed in these forward-looking statements due to a number of uncertainties and risks, including the risks described in this prospectus and other unforeseen risks. You should not put undue reliance on any forward-looking statements.

        We undertake no obligation to update forward-looking statements after we distribute this prospectus except as may be required under the federal securities laws.

USE OF PROCEEDS

        We estimate that the net proceeds of the sale of the 12,500,000 shares of common stock that we are selling in this offering will be $181.5 million, based on an assumed initial public offering price of $16 per share, the mid-point of the range on the front cover of this prospectus, and after deducting the estimated underwriting discounts and commissions and estimated offering expenses payable by us. If the underwriters' over-allotment option is exercised in full, we estimate that we will receive net proceeds of $209.5 million.

        We currently anticipate that we will use approximately $122.4 million of the net proceeds to prepay the entire principal, interest and prepayment penalty due on our $120.0 million senior second lien term loan and approximately $59.1 million to prepay a portion of the $379.0 million currently outstanding under our senior secured term loan B. We entered into the $120.0 million senior second lien term loan and the $380.0 million senior secured term loan B on March 17, 2004. The principal of the senior second lien term loan is due in a single installment on March 17, 2012, and bears interest either at a LIBOR rate plus 5% or a floating base rate determined by the lender plus 4%. The principal of the senior secured term loan B is subject to scheduled quarterly amortization of 0.25% of the initial principal amount, payable in arrears, for the first 6.75 years, and 93.25% of the initial principal in the final quarter of the seventh year, and bears interest either at a LIBOR rate plus a variable interest rate margin or a floating base rate determined by the lender plus a variable interest rate margin.

        We used the proceeds of these loans to refinance substantially all of our existing debt and pay accrued interest in the aggregate amount of $219.0 million, to pay fees and expenses of $11.0 million in connection with the new credit facilities and to make a cash payment in the aggregate amount of $270.0 million of which $258.4 million was distributed to our preferred and common stockholders, pro rata in accordance with their stockholdings, and $11.6 million was paid to management in the form of one-time bonuses. The purpose of the bonuses was to treat management equitably with other stockholders, by providing for a cash distribution to each individual based on the aggregate in-the-money value of his or her vested options. For additional information on these credit facilities including their terms and the use of their proceeds, see "Description of our Credit Facilities."

DIVIDEND POLICY

        We do not anticipate declaring or paying any cash dividends in the foreseeable future. The timing and amount of future cash dividends, if any, would be determined by our Board of Directors and would depend upon our earnings, financial condition and cash requirements at the time. See "Description of our Credit Facilities" for a discussion of restrictions in our credit facilities that may limit our ability to pay cash dividends in the future.

        In connection with our recent recapitalization on March 17, 2004, we distributed $258.0$258.4 million to our existing stockholders, pro rata on the basis of their relative ownership interests in the company. We do not intend to make similar distributions in the future.

CAPITALIZATION

        The following table sets forth our cash and cash equivalents and our consolidated capitalization at March 31, 2004:

•

on an actual basis; and



•

as adjusted to give effect to the following:



•

the automatic conversion of all outstanding shares of our preferred stock into 22,018,294 shares of our common stock upon closing ofimmediately prior to this offering;



•

the sale of 12,500,000 shares at an assumed initial public offering price of $16 per share, the midpoint of the range on the cover of this prospectus, after deducting underwriting discounts and commissions and estimated offering expenses payable by us; and



•

the use of proceeds to prepay the principal of and accrued interest and prepayment penalty on our $120.0 million senior second lien term loan and approximately $59.1 million to prepay a portion of the amount outstanding under our $380.0 million senior secured term loan B.

        You should read this table in conjunction with our consolidated financial statements and the notes thereto included elsewhere in this prospectus.

UNAUDITED PRO FORMA CONSOLIDATED FINANCIAL INFORMATION

        Our audited consolidated financial statements for fiscal 2004 are included elsewhere in this prospectus. The unaudited pro forma consolidated financial information presented herein should be read together with those financial statements and related notes and "Management's Discussion and Analysis of Financial Condition and Results of Operations."

        The unaudited pro forma consolidated financial information has been provided to enable readers to understand our historical financial results in relation to our recent recapitalization that occurred on March 17, 2004, and the sale of our common stock offered by this prospectus.

        Our historical March 31, 2004, balance sheet already reflects the financial impact of the recapitalization. We prepared the unaudited consolidated pro forma balance sheet to reflect the offering as if it had occurred on March 31, 2004. We prepared the unaudited pro forma consolidated statements of operations to reflect the recapitalization and the offering of our common stock as if such events had occurred on April 1, 2003.

        The pro forma consolidated balance sheet data at March 31, 2004, and statement of operations data for fiscal 2004, give effect to the recapitalization, the sale of 12,500,000 shares of our common stock at an assumed public offering price of $16 per share and the conversion of our preferred stock into 22,018,294 shares of our common stock immediately prior to the closing of this offering, along with the anticipated use of the estimated proceeds from this offering to prepay indebtedness and for other general corporate purposes.

        We have excluded $18.6 million of special charges, which includes $6.6 million in deferred finance costs, $11.6 million in one-time bonus payments to management and a related $0.4 million payroll charge in connection with the recapitalization, from our pro forma results of operations for fiscal 2004. For additional information on these one-time bonus payments, see "Use of Proceeds" and "Management—Executive Compensation."

        Certain information normally included in financial statements prepared in accordance with generally accepted accounting principles in the U.S. has been omitted pursuant to the rules and regulations of the SEC. The pro forma consolidated statement of operations data for fiscal 2004 are not necessarily indicative of results that would have occurred had the recapitalization and this offering been completed on April 1, 2003, and should not be construed as being representative of future results of operations. Likewise, the pro forma consolidated balance sheet data at March 31, 2004, is not necessarily indicative of our financial position at March 31, 2004, had the offering been completed on March 31, 2004.

(1)

Amount represents the elimination of compensation expense of $12.0 million, before taxes, incurred in connection with the March 17, 2004 recapitalization. For additional information on this payment, see "Use of Proceeds" and "Management—Executive Compensation."

(2)

Amount represents a net increase in interest expense of $11.0 million, before taxes, associated with the increased debt from the recapitalization, including $1.6 million of amortization for the increased deferred finance costs and the elimination of $2.0 million in amortization of deferred finance costs from the previous credit facility. For purposes of this calculation, the interest rates used were the actual rates (an average 4.8%) that existed at March 31, 2004.

(3)

Amount represents the elimination of special charges, before taxes, of $6.6 million in deferred finance costs related to the early extinguishment of debt in connection with the March 17, 2004 recapitalization.

(4)

Amount represents the income tax expense from (1), (2) and (3) above at our current 37% effective tax rate.

(5)

Amount represents reduced interest expense, before taxes, resulting from the anticipated use of the estimated proceeds from this offering to repay certain debt, of $2.0 million from a reduction of $59.1 million of senior secured term loan B, of $7.3 million from repayment of $120.0 million of senior second lien term loan and of $0.6 million reduction in amortization of deferred finance costs related to the debt that will be prepaid with the use of proceeds. For purposes of this calculation, the interest rates used were the actual rates (an average 4.6%) that existed at March 31, 2004.

(6)

Amount represents the income tax expense from (5) above at our current 37% effective tax rate.

(7)

Reflects the conversion of our preferred stock into 20,441,520 shares of common stock and the sale of 12,500,000 shares of common stock in the offering.

Unaudited

pro forma basic and diluted earnings per share have been calculated in accordance with the SEC rules for initial public offerings. These rules require that the weighted average share calculation give retroactive effect to any changes in our capital structure as well as the number of shares whose sale proceeds will be used to repay any debt as reflected in the pro forma adjustments. Therefore, pro forma weighted average shares for purposes of the unaudited pro forma basic earnings per share calculation consist of approximately 11,014,421 shares of common stock and 20,441,520 shares of converted preferred stock outstanding prior to this offering and 12,500,000 shares of our common stock being offered hereby.

(8)

The Company expectsWe expect to incur $2.4 million ($1.5 million net of tax benefit at our current 37% effective tax rate) of prepayment penalty and the write-off of deferred finance costs of $4.2 million ($2.7 million net of tax benefit at our current 37% effective tax rate) as a result of the offering. These expenses have been excluded from the pro forma statements of operations.

(9)

Reflects pro forma share data giving effect to the increase of 16,148,000 shares, which represents the number of shares that, when multiplied by an assumed offering price of $16, is sufficient to replace the capital in excess of earnings as a result of the distribution to shareholdersstockholders of $258.4 million in connection with our recapitalization.

(1)

Amount represents the deferred finance costs associated with the prepayment of debt.

(2)

Amounts represent the use of proceeds from this offering to prepay certain indebtedness.

(3)

Amount represents the splitreduction in accrued taxes attributed to the tax benefit on the prepayment penalty ($0.9 million) and write-off of common shares at a 28.5-for-1 ratio.deferred finance costs ($1.5 million).

(4)

Amount reflects the conversion of 772,572 shares of our preferred stock which represents the issuance amount plus a cumulative amount from the date of issuance to the date of conversion at a rate of 7.5% per year, compounded quarterly, and converted at a 28.5-for-1 ratio into 22,018,294 shares of common stock upon completion ofimmediately prior to this offering.

(5)

Amount represents the sale of 12,500,000 shares of common stock in this offering at an assumed initial public offering price of $16 per share, less related estimated expenses of $18.5 million, for net proceeds of $181.5 million.

(6)

Amount represents the $2.4 million ($1.5 million of tax benefit) prepayment penalty and $4.2 million ($2.7 million net of tax benefit) deferred finance costs associated with the prepayment of debt.

(7)

Amount represents the reduction in accrued taxes attributed to the tax benefit on the prepayment penalty ($0.9 million) and write-off of deferred finance costs ($1.5 million).

DILUTION

        At March 31, 2004, our net tangible book value (deficit) was $(143.0) million, or $(12.98) per share of common stock. Net tangible book value (deficit) per share is equal to our stockholders' equity (deficit) less goodwill and other intangible assets, divided by the total number of outstanding shares of our common stock. After giving effect to the sale of the shares of our common stock offered by us at an assumed initial public offering price of $16 per share, the mid-point of the range on the cover of this prospectus, and after deducting the underwriting discounts and commissions and estimated offering expenses payable by us, and the anticipated application of the proceeds from the offering, our net tangible book value at March 31, 2004, would have been $34.3 million, or $0.75 per share. This represents an immediate increase in net tangible book value of $13.73 per share to existing stockholders and an immediate dilution of $15.25 per share to new investors purchasing shares of our common stock in this offering.

        The following table illustrates the dilution per share:

        If the underwriters exercise their over-allotment option in full, the net tangible book value per share after giving effect to the offering would be $1.31 per share. This represents an increase in net tangible book value of $14.29 per share to existing stockholders and dilution in net tangible book value of $14.69 per share to new investors.

        The following table summarizes, as of March 31, 2004, the differences between the number of shares of common stock purchased from us, the total effective cash consideration and the average price per share paid by the existing stockholders and by the new investors purchasing stock in the offering at an assumed initial offering price of $16 per share, before deducting the estimated underwriting discounts and commissions and estimated offering expenses payable by us:

(1)

The total effective cash consideration paid by existing stockholders was $443.0 million,$447.1 million. The amount shown gives effect to the distribution of $258.4 million of which was distributed to existing stockholders as a return of capital in our recent recapitalization.

        If the underwriters exercise their over-allotment option in full, our existing stockholders would own 69.9% and our new investors would own 30.1% of the total number of shares of our common stock outstanding after this offering.

        The preceding discussion and table assumes no exercise of:

•

Stock options for 7,334,398 shares issuable upon exercise of outstanding options as of March 31, 2004, under our stock option plans at a weighted average exercise price of $13.63 per share; and



•

Stock options for 1,000,000 shares available for future grant or issuance under our stock option plans.2004 Equity Incentive Plan, and



•

1,000,000 shares issuable pursuant to our Employee Stock Purchase Plan.

        To the extent that any options are exercised, there will be further dilution to new investors. If all of our outstanding options as of March 31, 2004, had been exercised, the pro forma net tangible book value per share after this offering would have been $2.54 per share, representing an increase in pro forma net tangible book value of $15.52 per share to existing stockholders and a dilution in the pro forma net tangible book value of $13.46 per share to new investors.

SELECTED CONSOLIDATED FINANCIAL AND OPERATING DATA

        The following tables set forth certain selected consolidated financial and operating data. We were incorporated in October 2000 for the purpose of acquiring the Yuasa Inc. industrial battery business from Yuasa Corporation (Japan) and did not have any operations prior to October 1, 2000. Selected consolidated financial data for the periods prior to October 1, 2000, are derived from the consolidated financial statements of Yuasa Inc., which we refer to as the Predecessor Company. The summary consolidated financial data presented below for the three-year period ended March 31, 2004, and the balance sheet data at March 31, 2002, 2003 and 2004, have been derived from our consolidated financial statements which have been audited by Ernst & Young LLP, our independent auditors.registered public accounting firm. The summary consolidated financial data presented below as of and for the six months ended March 31, 2001 have been derived from audited financial statements that are not included in this prospectus. The summary consolidated financial data presented below as of and for the fiscal year ended March 31, 2000, and as of and for the six months ended September 30, 2000, have been derived from unaudited financial statements that are not included in this prospectus. You should read the selected financial data presented below in conjunction with our consolidated financial statements and the notes to our consolidated financial statements included elsewhere in this prospectus and "Management's Discussion and Analysis of Financial Condition and Results of Operations."